Airport surveillance may tighten after 29 passengers aboard two international flights were found to be hiding gold bullion in their rectums.

Customs officers made the discovery on Sunday at Madurai International Airport in Tamil Nadu, southern India.

The customs haul came to 10kg of gold, found on about 40 passengers on two flights from Colombo in Sri Lanka.

The customs probe found gold hidden in various places but the “ingenious way of concealment” – the rectum – seems to be gaining popularity, according to India’s Directorate of Revenue Intelligence (DRI) quoted by The Guardian.

Gold!

Incredibly, the rectal smugglers were allowed to walk free, as none was carrying enough gold individually to meet the criminal threshold.

Gold smuggling is common between Sir Lanka and India. Only a few weeks ago, a 45-year-old man heading for India was arrested at Colombo airport after customs officials noticed “suspicious movements”.

He was found to be carrying almost a kilogram of gold wrapped in four plastic bags and inserted into his rectum.

Because gold is a very heavy metal, the physical dimensions of gold bars are not great. A 10 ounce (311 gram) gold bar, for instance, is typically 60mm long by 35mm wide by 8mm thick. Note: those are millimetres, not centimetres. It’s worth about AUD 16,560.